Percentage Calculator
Work out percentages in seconds — find a percent of a number, compare two numbers, or measure increase and decrease.
Runs in your browser — your inputs never leave this device
What is X% of Y?
X is what percent of Y?
Percentage increase / decrease
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How to use the Percentage Calculator
- Choose the panel that matches your question — percent of a number, one number as a percent of another, or change between two numbers.
- Type your two values into the fields in that panel.
- Read the result instantly below the fields; it updates live as you type.
- Adjust any value to recalculate — there is no submit button and nothing is sent anywhere.
Frequently asked questions
How do I calculate X% of Y?
Multiply Y by X and divide by 100. For example, 20% of 150 is 150 × 20 ÷ 100 = 30. The first panel on this page does exactly this calculation.
Are my numbers uploaded or saved?
No. This calculator runs entirely in your browser — your inputs are never uploaded, logged or stored. All maths happens locally on your device.
How is percentage increase calculated?
Subtract the starting value from the new value, divide by the starting value, then multiply by 100. Going from 80 to 100 is (100 − 80) ÷ 80 × 100 = a 25% increase.
Why does the increase/decrease panel show an error when A is 0?
Percentage change is measured relative to the starting value. Dividing by zero is undefined, so a percentage change from 0 cannot be calculated — any move away from 0 is effectively an infinite relative change.
Can a percentage be more than 100%?
Yes. If X is larger than Y, then X is more than 100% of Y. Percentage increases can also exceed 100% — for example, going from 50 to 150 is a 200% increase.